While you can exclude the egg white, it will add to the structure and stability of the final sorbet. However, if you - as is recommended - plan on enjoying the sorbet right after it has been churned or very soon thereafter, you might as well leave out the egg white. Other means of getting a softer, not so hard-frozen sorbet include adding a little neutral alcohol (like vodka) or replacing some of the sugar in the recipe with inverted sugar (like corn syrup, agave nectar or honey).